599 FXUS66 KPQR 260932 AFDPQR Area Forecast Discussion National Weather Service Portland OR 232 AM PDT Tue Jul 26 2016 .SYNOPSIS...A weak upper trough near the coast with a weak westerly flow aloft over the Pacific Northwest will continue today into early Wednesday with morning low clouds giving way to afternoon sunshine and seasonable afternoon temperatures. An upper level ridge will build for the second half of the week and bring inland highs well into the 90s Thursday and Friday before the next trough arrives to moderate temperatures and increase clouds over the weekend. && .SHORT TERM...(Today through Thursday)...Another weak upper disturbance will move through the Pacific Northwest in a light westerly flow today, maintaining onshore flow. The models suggest more coverage of low clouds inland this morning as compared to Monday morning and the fog channel satellite imagery is supporting that trend. Don't believe they will fill the inland valleys, but there should be more coverage especially north but also some extending south along the Cascade foothills into parts of the central Willamette Valley. The clouds should burn back to near the coastline again today in the north and a bit offshore along the central Oregon coast today. Expect temps 4 to 6 degrees lower than Monday in the north valley but only a couple of degrees cooler at Eugene. The models show one last weak disturbance currently out near 40n/140w moving through southwest Washington and northwest Oregon later tonight and Wednesday morning. This should spread more low clouds onshore again Wednesday morning especially in the north, but coverage in the south is forecast to be a bit less. The models suggest pretty good clearing again Wednesday afternoon with some lingering low clouds along the north coast. The air mass warms a touch Wednesday and expect temps to warm close to those of Sunday and Monday in the south valley and approach those values in the north valley. The upper ridge builds some by Thursday with less coverage of morning low clouds Thursday morning, mainly north coast and locally inland along the Columbia River. The models indicate we have a good chance of seeing the first of a two day stretch of low to mid 90s inland on Thursday. Tolleson .LONG TERM...(Thursday night through Monday)...The models are showing one more very warm day on Friday but now with temps similar to those on Thursday, perhaps not quite as hot as previously thought as westerly flow continues and ridging is not quite as pronounced. The models are continuing to show an upper trough beginning to drop down the B.C. coast Saturday and swing through the Pacific Northwest Sunday and early next week. The ECMWF continues to be the weaker model with this pattern, but is getting closer to the GFS while the GFS is not quite as strong as it had been. This convergence of the models lends increasing confidence in a cool down this weekend, perhaps with some drizzle near the coast by Sunday. We will have to see whether we can sneak any showers out of this pattern early next week. Tolleson && .AVIATION...IFR to low end MVFR clouds have remained packed onto most of the coastal areas this evening. With onshore pres gradients generally stronger than the same time last night, expect MVFR marine clouds to spread into the north Willamette Valley late tonight and Tuesday morning. Lower confidence about other areas in the valley, but think KEUG will likely see an MVFR ceiling after 13Z as well. Expect whatever develops inland to break up and return to VFR conditions between 18Z and 21Z Tue. Along the coast MVFR and pockets of IFR cigs are likely to continue through the day Tue. KPDX AND APPROACHES...Marine clouds with MVFR cigs expected to develop late tonight and Tue morning between 12Z and 14Z, then break up again between 19Z and 21Z. Bowen && .MARINE...There will be little change the next several days as north winds persist over the waters and fresh swell remains the primary sea influence. The thermal induced trough of low pres will continue to expand slightly north in the afternoons and evenings for an increase in gusty winds, with the strongest pres gradients south of Cascade Head. Have issued a Small Craft Advisory for Winds with gusts 25-30 kt expected this afternoon through at least tonight across the waters off the central OR coast. The trough will expand further north Wed through Fri for continued small craft winds for the N OR/S WA waters in the afternoons and evenings. Seas around 6 ft tonight will remain in the 6-7 ft range through at least Wednesday, but will steepen later Tuesday as wind wave becomes dominant. Will have to keep an eye out for 7 ft/7 sec square seas as winds pick up later today, but will not issue an advisory for seas at this point. Bowen && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for winds from 3 PM this afternoon to 4 AM PDT Wednesday for Coastal Waters from Cascade Head OR to Florence OR out 60 nm. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
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